I don't know if anyone has suggested this yet. I didn't get a chance to read the whole thread. Something you might like to try is to think of it as an atemi. Rather than having your arm at an angle across their elbow, you can draw out their arm so that it is straight and have your arm parallel to theirs. Then hit them with a fingertip strike to the throat while stepping in. As they are responding to this, you can drop your arm and hit them in the nuts. It's not a nice way to do the technique, but it is something to have a play with. If you want to be really cruel, you could grab the jaw bone after the neck strike, but I wouldn't do that with anyone you want to train with again.